In recent years, Cullumber Company has purchased three machines. Because of frequent employee turnover in the accounting department, a different accountant was in charge of selecting the depreciation method for each machine, and various methods have been used. Information concerning the machines is summarized in the table below.

Machine

Acquired

Cost

$ $95,00087,00057,500$

Salvage Value

$ $12,00010,0007,500$

Useful Life $($in years$)$

$856$

Depreciation Method

Straight$-$line Declining$-$balance Units$-$of$-$activity

$1$ Jan. $1,2020$

$2$ July $1,2021$

$3$ Nov. $1,2021$

For the declining$-$balance method, Cullumber Company uses the double$-$declining rate. For the units$-$of$-$activity method, total machine hours are expected to be $25,000.$ Actual hours of use in the first $3$ years were $2021,500$; $2022,4,000$; and $2023,6,000.($a$1)$ For Machine #$3,$ calculate depreciable cost per hour under units of activity method. Depreciable cost $ per hour. $($a$2)$ Compute the amount of accumulated depreciation on each machine at December $31,2023.$ Accumulate. depreciation. $($b$)$ If machine $2$ was purchased on April $1$ instead of July $1,$ what would be the depreciation expense for this machine in $2021?$ in $2022?$